Problems with Tables in Oracle web DB

Actually I am facing a problem with Oracle Web DB, the problem is associated with table creation. At first when I was working on the table and creating them by using PL/SQL, they were working fine and data was updating smoothly. But I face one problem when I was updating one table by taking entries from other two tables I was not getting desired results. But the same query was working with other tables. But I don't find any technical or conceptual mistake in tables at that time. For rectifying this problem I deleted all the tables and generated them again. Now there is another problem, whenever I update a table with new data it doesn't take any data and gives message "No Rows Returned", I have checked all my code and procedures but the problem remains. Can anyone help me in this problem and trace the exact problem ? I'll be highly oblised.